Dust dissemination poses safety, health and environmental problems in many environments. Dust particles, both inhalant (up to 30μ) and respirable (up to 10μ), are known to contaminate food and water, and when inhaled, can result in serious respiratory ailments. In other cases, the presence of coal dust may lead to possible spontaneous combustion. Similar concerns are raised in other mining, chemical, steel and waste industries which generate smoke, dust, ash and other particulate matters. Dust emission is also a problem during road construction and the transportation of coal or pulverised minerals in railway cars or trucks.
The usual method for allaying dust is to apply a water spray either with a fixed or mobile pressurised spray system, gravity fed distribution or by water cannon. Water trucks are commonly used, for example, on mine haulage roads, quarry access, road constructions, unsealed roads and other types of dusty areas supporting traffic. The main problem with using water sprays is that the dust is controlled only for a short period of time depending on climatic conditions. This is particularly the case during road construction where application of the water spray has to be constantly repeated with a frequency of up to every hour or less to provide effective dust control. Even then, the dust abatement performance is often poor and there is a need for ready access to water, which can be particularly difficult to obtain during droughts.
Various methods have been employed to date in knock down dust suppressants and dust dissemination. Incorporation of hygroscopic salts such as calcium or magnesium chloride in the water sprays is often done in an attempt to retain moisture on the dusty surface, but the method is often disadvantageous due to high salt usage rates, moisture scavenging properties and equipment corrosion. Oil and oil-based emulsions, pine resin tall oil, and lignosulfonate as a by-product of paper-mills have been used for dust control purposes. See for example U.S. Pat. No. 4,417,992 which discloses the use of oil-containing emulsions comprising light paraffin solvents, water and cross-linked polymers for dust control. U.S. Pat. No. 4,746,543 discloses the use of an aqueous solution containing a mixture of water soluble acrylic polymers with water soluble non-ionic glycol polymers with sulfonate nonionic surfactants and co-surfactants as dust control agents. U.S. Pat. No. 4,594,268 discloses the use of an aqueous emulsion of methacrylate polymer as a dust control agent. U.S. Pat. No. 5,194,174 describes the use of non-viscous water based solutions including a polyvinyl alcohol and boric acid for suppressing dust. U.S. Pat. No. 4,801,635 describes a combination of water-soluble anionic acrylic polymers in combination with water-soluble non-ionic glycol polymers in an aqueous medium together with sulfonate surfactants for the control of dust emissions into the environment. U.S. Pat. No. 5,256,444 describes the control of fugitive dust emissions by the application of a water-soluble cationic polymer solution with a foaming agent. European Patent No. 0 134 106 describes compositions for dry dusty soil surface treatment and stabilisation of surface soil by application of an aqueous emulsion of homopolymers and copolymers of acrylic acid and a polybasic salt including surfactants and wetting agents.
Notwithstanding that there is a wide variety of dust suppressant compositions and methods available, there is a need for new, improved or at least alternative dust suppressant compositions for use in knocking down airborne dust and controlling fugitive dust emissions in the road building, waste control, mining, haulage and related industries. For example, road construction companies often revert back to the use of simple but generally ineffective water sprays rather than using aqueous suppressant compositions with durable dust control effect.